Recent guidelines require that children beneath a selected age and/or size not be subjected to impact by front airbags. In some vehicles, manual switches are provided to deactivate airbag deployment systems when a child restraint seat is occupied by a child. A driver or passenger can forget to operate the manual switch when a child is seated, or the airbag can be left in a deactivated mode when an adult is seated. This has led to arrangements for automatically deactivating airbags when the presence of a child rather than an adult in a vehicular seat is detected.
The threshold for enabling or suppressing air bag deployment is dependent on the design and calibration of the suppression system used. In systems where the occupant is classified based on a measure of the force applied to the seat, it can be difficult to reliably distinguish between a normally seated adult and a tightly belted car seat. If the seat belt is unduly tightened, it can create an additional downward force on the seat, creating an erroneous weight reading. In other words, a normally seated adult and a tightly belted car seat may apply a similar force on the seat.